console: support /pagespeed_console

sligocki is adding a feature to pagespeed where it will parse your statistics
for you and determine if there are any problems.  This CL wires up the
ConsoleHandler and also includes a few required files in the build process.

It doesn't work yet, because as of svn r3193 the console has a hardcoded json
request to '/mod_pagespeed_statistics' and in nginx we use '/ngx_...' .
I've tested this by changing all uses here to use the "mod_..." version and that
worked, but I've undone those changes.
Merge pull request #415 from pagespeed/jefftk-console

console: support /pagespeed_console